1. Field of the Invention
The present invention relates generally to a plug-in wire connection terminal structure, and more particularly to a plug-in wire connection terminal structure, which has simplified structure and is easy to assemble. Moreover, the plug-in wire connection terminal structure has excellent structural strength and is able to provide excellent elastic holding effect.
2. Description of the Related Art
There are various conventional large-current connectors. For example, Chinese Invention Patent Publication No, CN 101595603A discloses an electrical wire connection terminal. The terminal has an insulation housing, a metal piece disposed in the housing and a leaf spring disposed in the housing. The metal piece is made of high-conductivity metal material and the leaf spring has highly stable elasticity. The metal piece is assembled with the leaf spring to forma conduction circuit for conducting large current. The metal piece has a connection plate. Two sides of the connection plate are bent to form a latch arm and a contact arm respectively. A plug section and a fixing section respectively extend from two end sections of the contact arm. A fixing section corresponding to the plug section extends from one side of the latch arm opposite to the plug section. A locking protrusion section is disposed on the fixing section and stopper sections are disposed on two sides of the fixing section. The middle section of the leaf spring is formed with a bight section. One side of the bight section is formed with an outward protruding latch section, which is correspondingly latched with the fixing section of the metal piece. A support arm further extends from the bight section for more securely latching with the metal piece. The support arm is formed with a hollow in which the fixing section of the metal piece is fitted. Moreover, the latch section is formed with a hole. The other side of the leaf spring is formed with a clamping arm. The end of the clamping arm extends through the hollow of the support arm to abut against the inner face of the contact arm. When assembled, the fixing section of the metal piece is fitted in the hollow of the leaf spring and the latch section of the leaf spring is inserted between the fixing section of the metal piece and the stopper sections. The locking protrusion section is inserted into the corresponding hole, whereby the leaf spring can be securely connected with the metal piece with the end section of the clamping arm abutting against the contact arm.
In practice, the insulation housing is formed with a conductor inlet and an operation hole corresponding to the hollow of the leaf spring. The operation hole is positioned above the conductor inlet. An electrical conductor can extend into the conductor inlet to upward push the clamping arm, whereby the end section of the clamping arm can obliquely abut against the electrical conductor to hold and prevent the electrical conductor from being reversely pulled out. Accordingly, the electrical conductor can keep in tight electrical contact with the contact arm of the metal piece. The plug section can be electrically plugged into an external corresponding socket. An operation tool (such as a screwdriver) can extend into the operation hole to shift the clamping arm and separate the end section of the clamping arm from the electrical conductor. Under such circumstance, the electrical conductor can be reversely pulled out of the conductor inlet and separated from the metal piece.
In practice, the above structure has the following shortcomings:                1. The leaf spring and the metal piece are designed with complicated configuration and structure so that the development and processing cost is higher. This will affect the competitive ability of the product due to higher price.        2. The end section of the support arm and the latch section of the leaf spring are fixed with the metal piece for assembling therewith. In addition, the clamping arm needs to intersect the hollow of the support arm. Therefore, total length of the leaf spring is longer and it is necessary to use and cut off a mass of metal material to manufacture the leaf spring. As a result, the manufacturing cost can be hardly lowered as a whole.        3. The support arm of the leaf spring is formed with a large hollow so that amass of waste material is produced during the processing procedure. This fails to meet the principle of economic efficiency.        
There also are various plug-in wire connection terminal structures. For example, Chinese Utility Patent Publication No. CN 201112705Y discloses a plug-in wire connection terminal. The terminal includes a pin-shaped plug-in terminal (metal plug-in terminal) and a pin-shaped socket member (metal connection socket member). The pin-shaped socket member has a through hole for receiving the pin-shaped plug-in terminal. At least one split is formed on the annular wall of the pin-shaped socket member, whereby the through hole is expandable. In addition, the outer wall of the middle section of the pin-shaped socket member is formed with an annular recessed section for a spring steel collar to fit around the pin-shaped socket member. By means of the elasticity of the spring steel collar, the through hole is fully elastically bound to have a sufficient structural strength. Accordingly, it is ensured that the pin-shaped plug-in terminal is lastingly tightly enclosed in the pin-shaped socket member.
Chinese Utility Patent Publication No. CN 201038406Y discloses a power connector terminal structure including a female terminal in which a male terminal can be electrically plugged. The female terminal is composed of a main body and an outer housing. The main body is formed with a locating section, which can be fixedly disposed in a preset insulation seat body. A welding section is disposed on one side of the locating section. The welding section can extend through the insulation seat body to outer side thereof. The other side of the locating section distal from the welding section is formed with a mating section. The mating section has at least one axially extending split. In addition, an annular groove is formed on outer circumference of the mating section for the outer housing to fit thereon. A restriction section is disposed on one side of one end of the outer housing. The restriction section can be inserted in the split to provide a fixing effect for preventing the outer housing from axially rotating on the surface of the annular groove. Also, the outer housing permits the mating section to elastically expand without over-stretching. Accordingly, a true locating effect is achieved to keep a good electrical connection.
However, in the above conventional structures, the outer circumference of the middle section of the pin-shaped socket member (or the female terminal) is formed with an annular recess (annular groove) for fitting a spring steel collar (outer housing) around the outer circumference. In practice, the conventional structures have the following shortcomings:                1. The outer circumference of the middle section of the pin-shaped socket member (or the female terminal) is formed with the annular recess (annular groove). In this case, the pin-shaped socket member (or the female terminal) has a complicated configuration and structure. This will increase difficulty in forming and processing the pin-shaped socket member (or the female terminal). As a result, the manufacturing cost is increased and the competitive ability is lowered due to higher price.        2. In design, it must be ensured that the inner circumference of the spring steel collar or the outer housing is snugly fitted on the annular recess or annular groove in dimension. Otherwise, in the case of unfitness, the holding force will be insufficient (the size of the inner circumference of the spring steel collar or the outer housing is too large) or the elastic expansion of the pin-shaped socket member or female terminal is insufficient (the size of the inner circumference of the spring steel collar or the outer housing is too small). Such requirement in dimension precision will also cause increase of manufacturing cost.        3. The spring steel collar (or the outer housing) is a partially split structure with a C-shaped cross section. When assembled, the split is directly fitted onto the annular recess (or the annular groove). In such assembling process, in the case that the spring steel collar (or the outer housing) itself has weaker structural strength, it is easier to expand the spring steel collar (or the outer housing) to overpass the outer circumference of the pin-shaped socket member (or female terminal) with larger outer diameter. In this case, the spring steel collar (or the outer housing) can be easily assembled on the annular recess (or annular groove). However, such spring steel collar (or the outer housing) will inevitably have poorer elasticity so that the holding force applied to the pin-shaped socket member (or the female terminal) is easy to deteriorate. Reversely, in the case that the spring steel collar (or the outer housing) has greater structural strength, then the spring steel collar (or the outer housing) will have better structural elasticity. However, under such circumstance, it will be uneasy to assemble the spring steel collar (or the outer housing) on the annular recess (or annular groove). Accordingly, in consideration of structural design, it is hard to decide whether the difficulty in assembling should be lowered or the holding force should be increased.        
It is therefore tried by the applicant to provide a plug-in wire connection terminal structure to overcome the shortcomings existing in the conventional technique.